This competing continuation of the six site Child/Adolescent Anxiety Multimodal Treatment Study (CAMS), which is currently in year 3 of the 4 year award, is being submitted in response to PA-01-123 inviting collaborative research on Clinical Studies of Mental Disorders. Anxiety disorders are among the most common conditions affecting youth with point prevalence of 12-20%. The three most common childhood onset anxiety disorders, separation anxiety disorder (SAD), generalized anxiety disorder (GAD) and social phobia (SP), routinely co-occur and cause clinically significant impairment in academic, social, and family functioning. Left untreated, they foretell persistent anxiety, major depression and substance abuse into adulthood. Hence, effective treatments for childhood-onset anxiety disorders promise to alleviate and perhaps to prevent morbidity and even mortality. In randomized controlled trials, members of our group have shown that cognitive-behavioral therapy (CBT) and the selective serotonin reuptake inhibitors (SSRIs) are effective for anxiety disorders in youth. To date there are no controlled trails comparing CBT and an SSRI, alone and in combination, to a suitable control condition in the same patient population. CAMS is a two phase, masked, randomized controlled trial for youth ages 7-17 years with SAD, SP and GAD. Phase I is a 12-week, acute efficacy study; subjects are randomized (2:2:2:1) to CBT, sertraline, their combination or pill placebo. Phase II involves a 6-month maintenance phase for Phase I responders. We employ manualized intervention and assessment protocols, including the assessment of adverse events, and state-of-the-art quality assurance procedures that insure uniform cross-site administration of the study protocol. All subjects are evaluated at all assessment points for both beneficial and adverse outcomes. Assessments include parent, child and clinician ratings; to preserve study blindness, the primary outcomes are assessed by blind independent evaluators. The proposed competing continuation, which builds on demonstrated feasibility in sample recruitment and retention, will extend CAMS for 24 months and expand the CAMS sample from 318 to 478 subjects to increase power (1) to precisely estimate effect size differences on the primary dependent measures and (2) to promote the identification of subgroup differences (moderator analyses) and mechanisms of treatment response (mediator analyses).